1. Field of the Invention
This invention relates generally to footwear, and more particularly to an article of footwear having a cushioning member disposed therein which provides enhanced cushioning properties to the article of footwear.
2. Description of Related Art
One of the problems associated with shoes has always been striking a balance between support and cushioning. Throughout the course of an average day, the feet and legs of an individual are subjected to substantial impact forces. Running, jumping, walking and even standing exert forces upon the feet and legs of an individual which can lead to soreness, fatigue, and injury.
The human foot is a complex and remarkable piece of machinery, capable of withstanding and dissipating many impact forces. The natural padding of fat at the heel and forefoot, as well as the flexibility of the arch, help to cushion the foot. An athlete""s stride is partly the result of energy which is stored in the flexible tissues of the foot. For example, during a typical walking or running stride, the achilles tendon and the arch stretch and contract, storing energy in the tendons and ligaments. When the restrictive pressure on these elements is released, the stored energy is also released, thereby reducing the burden which must be assumed by the muscles.
Although the human foot possesses natural cushioning and rebounding characteristics, the foot alone is incapable of effectively overcoming many of the forces encountered during athletic activity. Unless an individual is wearing shoes which provide proper cushioning and support, the soreness and fatigue associated with athletic activity is more acute, and its onset accelerated. This results in discomfort for the wearer which diminishes the incentive for further athletic activity. Equally important, inadequately cushioned footwear can lead to injuries such as blisters, muscle, tendon and ligament damage, and bone stress fractures. Improper footwear can also lead to other ailments, including back pain.
Proper footwear should complement the natural functionality of the foot, in part by incorporating a sole (typically, an outsole, midsole and insole) which absorbs shocks. However, the sole should also possess enough resiliency to prevent the sole from being xe2x80x9cmushyxe2x80x9d or xe2x80x9ccollapsing,xe2x80x9d thereby unduly draining the energy of the wearer.
In light of the above, numerous attempts have been made over the years to incorporate means into a shoe which provides improved cushioning and resiliency to the shoe. For example, attempts have been made to enhance the natural elasticity and energy return of the foot by providing shoes with soles which store energy during compression and return energy during expansion. These attempts have included using compounds such as ethylene vinyl acetate (EVA) or polyurethane (PU) to form midsoles. However, foams such as EVA tend to break down over time, thereby losing their resiliency.
Another concept practiced in the footwear industry to improve cushioning and energy return has been the use of fluid-filled devices within shoes. The basic concept of enhancing cushioning and energy return by transferring a pressurized fluid between the heel and forefoot areas of a shoe is known. U.K. Patent No. 338,266 to Rayne, U.S. Pat. No. 547,645 to Lacroix, U.S. Pat. No. 1,069,001 to Guy, U.S. Pat. No. 2,080,499 to Nathanson, and U.S. Reissue Pat. No. 34,102 to Cole, each disclose the basic concept of having cushions containing pressurized fluid disposed adjacent the heel and forefoot areas of a shoe. Each of these technologies presents its own complications. However, the overriding problem common to each of these technologies is that the cushioning means taught therein are inflated with a fluid under pressure. Each of the above-noted patents discloses a cushioning means wherein a pressurized gas is forced into the cushioning means, usually through a valve accessible from the exterior of the shoe.
There are several difficulties associated with using a pressurized fluid within a cushioning device. Most notably, it may be inconvenient and tedious to constantly adjust the pressure or introduce a fluid to the cushioning device. Moreover, it is difficult to provide a consistent pressure within the device thereby giving a consistent performance of the shoes. In addition, a cushioning device which is capable of holding pressurized gas is comparatively expensive to manufacture. Further, pressurized gas tends to escape from such a cushioning device, requiring the introduction of additional gas. Finally, a valve which is visible to the exterior of the shoe negatively affects the aesthetics of the shoe, and increases the probability of the valve being damaged when the shoe is worn.
A cushioning device which, when unloaded contains air at ambient pressure provides several benefits over similar devices containing pressurized fluid. U.S. Pat. No. 2,100,492 to Sindler and U.K. Patent Application No. 2,039,717 to Karhu-Titan both disclose the use of a cushioning device containing ambient air. However, neither of these patents provides for the transfer of air between the heel and forefoot portions of the shoe.
German Patent No. 820,869 to Weinhardt et al. and U.S. Pat. No. 4,577,417 to Cole both appear to disclose a cushioning device having heel and forefoot cavities containing ambient air. The Weinhardt et al. patent appears to disclose a pneumatic shoe warmer insert equipped with two air chambers joined by a tube. The Cole patent discloses a sole and heel structure having premolded bulges connected by a passageway, wherein air at atmospheric pressure is disposed within the sole and heel structure.
The technologies taught in these patents do not provide for more than one rate or type of air flow between the cavities. Both these patents show a cushioning device having merely a straight xe2x80x9ctubexe2x80x9d passageway which connects the cavities of the device. This straight xe2x80x9ctubexe2x80x9d structure results in the passageways providing only one rate or type of air flow between the cavities. Neither the Cole patent nor the Weinhardt et al. patent discloses a cushioning device which may be customized for different types of activities and body weights.
A similar disadvantage is present in U.S. Pat. No. 4,458,430 to Peterson. The Peterson patent describes a cushioning device having cushions disposed beneath the heel and front transverse arch of the foot. The cushions are partially or completely filled a fluid, which may be of varying viscosities. Similar to the above-noted devices, a major deficiency of the Peterson device is that the channels connecting the cushions are merely straight xe2x80x9ctubexe2x80x9d channels, of a uniform diameter throughout their length. As previously indicated, this structure has the disadvantage of providing only one amount or degree of cushioning, which cannot be tailored or modified to accommodate different athletic activities and body types.
Although attempts have been made to create valve means which can control or, vary the rate of fluid flow, such attempts have resulted in overly cumbersome, complex and expensive structures. U.S. Pat. No. 4,446,634 to Johnson et al. shows an article of footwear having heel and ball bladders, two conduits connecting the bladders, and valves disposed on the conduits. By rotating knobs attached to the valves, the rate of fluid flow between the bladders can be regulated. In addition to the difficulties associated with pressurized fluid, the Johnson et al. patent suffers from several other shortcomings. Most prominent among these are that the numerous parts and intricate interrelationship thereof results in a cushioning member which is expensive to manufacture, and prone to malfunction.
PCT Application No. PCT/GB91/00740 (International Publication No. WO 91/16831) to Seymour teaches valve means comprising two ribbed members formed from a stiff plastic which are disposed above and beneath a capillary tube. Because the ribbed members of the Seymour device are formed of a different material than the cushioning member thereof, the cost of manufacturing the device is increased. In addition, the ribbed members are designed to xe2x80x9cpinchxe2x80x9d the capillary tube closed entirely during use, which can prevent an adequate amount of fluid from reaching the forefoot container prior to forefoot strike. Further, the capillary tube of the Seymour device merely comprises a straight tube, and thus shares the inadequacies of other devices discussed herein which possess the same feature.
Accordingly, prior to the development of the present invention, there was not a shoe which incorporated a cushioning member containing ambient air, wherein the cushioning member included a communication channel having impedance means disposed therein which served to restrict the flow of air between distinct chambers. In addition, prior to the development of the present invention, there was not a shoe which taught altering the structure of the impedance means, such that differently-sized and shaped impedance means provided varying types of air flow between the chambers, and consequently provided varying degrees of cushioning. Further, those shoes which have attempted to use fluid-filled devices incorporating valve means to cushion the foot of a wearer have had such drawbacks as adding increased weight to the shoe, providing inadequate and uneven cushioning, and being inordinately complex and expensive to manufacture.
Therefore, it is an object of the present invention to provide an article of footwear having enhanced cushioning and energy-returning characteristics.
It is a further object of the present invention to provide an article of footwear having a cushioning member containing ambient or slightly pressurized air.
It is a further object of the present invention to provide an article of footwear having a cushioning member with impedance means which restricts the flow of air between chambers.
It is a further object of the present invention to provide an article of footwear having a cushioning member which is capable of providing varying amounts or degrees of cushioning.
It is a further object of the present invention to provide an article of footwear having a cushioning member which will maintain its cushioning characteristics throughout the life of the shoe.
It is a further object of the present invention to provide an article of footwear having a cushioning member surrounded by a stablizing rim and covered by a moderator which enhances the cushioning characteristics of the cushioning member.
It is a further object of the present invention to provide an article of footwear having a cushioning member which may easily be incorporated in either a left or a right shoe without modification to the member.
It is a further object of the present invention to provide an article of footwear having a cushioning member which is simple and inexpensive to manufacture.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention as embodied and broadly described herein, the article of footwear of the present invention comprises a sole and a resilient cushioning member containing air at ambient pressure disposed within the sole. The cushioning member includes a first chamber, a second chamber and a communication chamber connecting the first and second chambers. The communication chamber has an average cross-sectional area which is less than the average cross-sectional area of both the first and second chambers. Impedance means for restricting the flow of air between the first and second chambers is disposed within the communication chamber and has an average cross-sectional area less than the remainder of the communication chamber.
The sole may comprise a midsole having a cavity portion, wherein the cushioning member is disposed within the cavity portion. Alternatively, the sole may comprise an outsole having a cavity portion, wherein the cushioning member is disposed therein. The sole may also comprise an insole having a cavity portion, wherein the cushioning member is disposed therein. The article of footwear may further comprise a sockliner having a cavity portion disposed within a upper, wherein the cushioning member is disposed within the cavity portion of the sockliner.
The cushioning member may be formed of a blow-molded elastomeric material. The article of footwear may further include a moderating member disposed above the cushioning member for defusing impact forces upon the cushioning member and providing support to the foot of a wearer. The moderating member may be formed of a material having a Shore A hardness of 75-95 or Shore C hardness of 55-75. The moderating member may be integral with the sole of the article of footwear.
The sole of the present invention may further comprise a heel portion and a forefoot portion, and the first and second chambers of the cushioning member may be disposed adjacent the heel and forefoot portions of the sole, respectively. Flexure grooves may be disposed on the second chamber of the cushioning member. A partition may be disposed on one of the first and second chambers for altering the direction of the air flow within the cushioning member.
The impedance means of the present invention may be substantially hourglass-shaped, or, alternatively, may be substantially xe2x80x9czxe2x80x9d-shaped, substantially xe2x80x9cwxe2x80x9d-shaped, or substantially xe2x80x9csxe2x80x9d-shaped.
The cushioning member may further comprise an upper portion and a lower portion which are mirror images of one another, such that the cushioning member may be readily disposed in either a left shoe or a right shoe.
Alternatively, the article of footwear of the present invention comprises a sole having a heel portion, an arch portion and a forefoot portion, and a cavity portion formed within the sole extending substantially from the heel portion to the forefoot portion thereof. A non-permeable, resilient first chamber containing ambient air is disposed within the cavity portion adjacent the heel portion. A non-permeable, resilient second chamber containing ambient air is disposed within the cavity portion adjacent the forefoot portion. A non-permeable communication chamber containing ambient air is disposed within the cavity portion adjacent the arch portion, and connects the first and second chambers. Impedance means is disposed within the communication chamber and has an average cross-sectional area which is smaller than the average cross-sectional area of the remainder of the communication chamber. The impedance means restricts the flow of air between the first and second chambers and provides enhanced cushioning to the article of footwear by controlling the velocity at which the air moves between the first and second chambers.
The article of footwear may be formed of an unitary piece of blow-molded elastomeric material. The impedance means may increase the velocity and turbulence of the air as it moves between the first and second chambers. The communication chamber may be sized and shaped to provide turbulent air flow between the first and second chambers when the weight of a wearer applies downward pressure to the first chamber. Alternatively, the communication chamber may be sized and shaped to provide laminar air flow or transitional air flow between the first and second chambers when the weight of a wearer applies downward pressure to the first chamber.
Ridges may be disposed on the upper and lower surfaces of the communication chamber. The vertical distance between the upper and lower surfaces of the second chamber may be less than the vertical distance between upper and lower surfaces of the first chamber.
A moderating member may be disposed above the cavity portion for diffusing impact forces upon the cushioning member and for providing support to the foot of a wearer. The sole of the present invention may further comprise an upper surface and a lower surface, wherein the cavity portion is formed within the lower surface of the sole, and the moderating member comprises the upper surface of the sole.
Alternatively, the article of footwear of the present invention may comprise a sole and a resilient cushioning member containing pressurized air disposed within the sole. The cushioning member includes a first chamber, a second chamber. and a communication chamber connecting the first and second chambers. The communication chamber has an average cross-sectional area which is less than the average cross-sectional area of both the first and second chambers. Impedance means for restricting the flow of air between the first and second chambers is disposed within the communication chamber and has an average cross-sectional area which is less than the remainder of the communication chamber.